GMC T Series 1994 Repair Manual page 849

N O T IC E : W h e n f a s t e n e r s a r e r e m o v e d , a lw a y s r e in s t a ll th e m a t th e s a m e lo c a t io n f r o m w h ic h t h e y w e r e
r e m o v e d . I f a f a s t e n e r n e e d s to b e re p la c e d , u s e th e c o r r e c t p a r t n u m b e r f a s t e n e r f o r t h a t a p p lic a t io n . I f
th e c o r r e c t p a r t n u m b e r f a s t e n e r is n o t a v a ila b le , a f a s t e n e r o f e q u a l s iz e a n d s t r e n g t h ( o r s t r o n g e r ) m a y
b e u s e d . F a s t e n e r s t h a t a r e n o t re u s e d , a n d t h o s e r e q u ir in g t h r e a d lo c k in g c o m p o u n d w ill b e c a lle d o u t.
T h e c o r r e c t t o r q u e v a lu e m u s t b e u s e d w h e n in s t a llin g fa s t e n e r s t h a t r e q u ir e it. I f t h e a b o v e c o n d it io n s
a r e n o t f o llo w e d , p a r t s o r s y s t e m d a m a g e c o u ld re s u lt.
SUBJECT
General D escription..................................................................................................................................................... 7D2- 1
Model 2 4 1 .................................................................................................................................................................... 7D2- 1
Identification........................................................................................................................................................... 7D2- 1
Power F lo w ............................................................................................................................................................. 7D2- 1
Disassem bly.................................................................................................................................................................... 7D2- 2
External Com ponents...............................................................................................................................................7D2- 2
Mainshaft Extension and Oil Pump H ousing................................................................................................... 7D2- 2
Internal Com ponents................................................................................................................................................ 7D2- 2
Cleaning and Insp ectio n.............................................................................................................................................7D2- 7
A ssem bly......................................................................................................................................................................... 7D2- 7
Bearing and Seal Replacem ent............................................................................................................................ 7D2- 7
Internal Com ponents................................................................................................................................................7D2- 8
External Com ponents...............................................................................................................................................7D2-10
S pecifications.................................................................................................................................................................7D2-13
Fastener Tightening Specifications......................................................................................................................7D2-13
Lubrication Specifications...................................................................................................................................... 7D2-13
Special T o o ls ..................................................................................................................................................................7D2-14
MODEL 241
The Model 241 transfer case is a chain-driven,
four-position unit providing four-wheel drive high and
low ranges, a two-wheel high range, and a neutral posi­
tion. The Model 241 is a part-time four-wheel drive unit.
Torque input in four-wheel high and low ranges is undif­
ferentiated. The range positions are selected by a
floor-mounted gearshift lever.
The Model 241 has a two-piece aluminum case con­
taining front and rear output shafts, two drive sprockets,
a shift mechanism, and a planetary gear assembly. The
drive sprockets are connected and operated by the
drive chain. The planetary assembly which, consists of
a six-pinion carrier and an annulus gear provides the
four-wheel drive low range when engaged. The gear
reduction ratio is 2.72:1 in this range (figures 1 and 2).
IDENTIFICATION
An identification tag is attached to the rear half of the
transfer case (figure 2). This tag provides the transfer
case model number, low range reduction ratio, and an
SECTION 7D2
NEW PROCESS 241
TRANSFER CASE
CONTENTS
GENERAL DESCRIPTION
assembly number. The information on this tag is neces­
sary for servicing this transfer case. If the tag is
removed or becomes dislodged during service opera­
tions, be sure to keep the identification tag with the unit.
POWER FLOW
In all drive range positions input torque is transmitted
to the transfer case gear train through the transfer case
input gear.
In 2HI range, torque is transmitted from the input gear
to the range shift hub and mainshaft. Torque flow con­
tinues through the slip yoke which is splined to the
mainshaft, and finally to the rear propeller shaft and
axle. In 2HI range, the mode synchronizer remains in
the neutral position and does not lock the drive sprock­
et to the mainshaft. As a result, torque is not transferred
to the driven sprocket.
In 4HI range, torque from the input gear is transmitted
to the mainshaft in exactly the same fashion as in the
2HI range. However, in 4HI position, the mode synchro­
nizer sleeve is shifted into engagement with the clutch
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